It seems that something with omniauth kerberos has changed in version 12.x. Ever since the upgrade the kerberos login panel is missing.
edit: It seems the Kerberos panel is supposed to be missing now, and Kerberos works in the “Standard” panel. UNLESS you are using Mac Chrome. In Chrome you fail to see the Kerberos name field hint and the login does not work. Safari and Firefox seem to work just fine. I will be clearing cache and stuff and will report back if that makes any difference.
edit: Clearing cache resolved issue